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    <title>Document</title>
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    <script>
        //五种基本数据类型
        let num = 1;
        let str = "";
        let bool = true;
        let und = undefined;
        let nul = null;

        console.log(typeof num);//
        console.log(typeof str);//
        console.log(typeof bool);//
        console.log(typeof und);//
        console.log(typeof nul);//

        console.log("====");//

        //引用数据类型 object function Symbel BigInt
        let obj = {};
        let fn = function(){};
        let arr = [];

        //原始数据类型
        let sy = Symbol('abc');//生成唯一的字符串
        let big1 = 300000000n;//超越原有js中可处理的最大数值
        let big2 = 200000000n;//超越原有js中可处理的最大数值

        console.log(typeof obj)
        console.log(typeof fn)
        console.log(typeof arr)
        console.log(typeof sy)
        console.log(typeof big1)
        console.log(big1 + big2)

        console.log("====");//

        //bigdecimal js

        let a = new Array(2000);//强引用
        //没有对象引用时，垃圾回收机制会回收该空间
        //a = null;//取消引用
        //a被某个对象包含，是弱引用
        //b = a，强引用

    </script>
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